diff --git a/lib/stripe/api_requestor.rb b/lib/stripe/api_requestor.rb
index c4d8a93f6..78c927b1a 100644
--- a/lib/stripe/api_requestor.rb
+++ b/lib/stripe/api_requestor.rb
@@ -195,23 +195,29 @@ def request
 
     def execute_request(method, path, base_address,
                         params: {}, opts: {}, usage: [])
-      params = params.to_h if params.is_a?(RequestParams)
-      http_resp, req_opts = execute_request_internal(
-        method, path, base_address, params, opts, usage
-      )
-      req_opts = RequestOptions.extract_opts_from_hash(req_opts)
+      old_requestor = self.class.current_thread_context.active_requestor
+      self.class.current_thread_context.active_requestor = self
+      begin
+        params = params.to_h if params.is_a?(RequestParams)
+        http_resp, req_opts = execute_request_internal(
+          method, path, base_address, params, opts, usage
+        )
+        req_opts = RequestOptions.extract_opts_from_hash(req_opts)
 
-      resp = interpret_response(http_resp)
+        resp = interpret_response(http_resp)
 
-      # If being called from `APIRequestor#request`, put the last response in
-      # thread-local memory so that it can be returned to the user. Don't store
-      # anything otherwise so that we don't leak memory.
-      store_last_response(object_id, resp)
+        # If being called from `APIRequestor#request`, put the last response in
+        # thread-local memory so that it can be returned to the user. Don't store
+        # anything otherwise so that we don't leak memory.
+        store_last_response(object_id, resp)
 
-      api_mode = Util.get_api_mode(path)
-      Util.convert_to_stripe_object_with_params(resp.data, params, RequestOptions.persistable(req_opts), resp,
-                                                api_mode: api_mode, requestor: self,
-                                                v2_deleted_object: method == :delete && api_mode == :v2)
+        api_mode = Util.get_api_mode(path)
+        Util.convert_to_stripe_object_with_params(resp.data, params, RequestOptions.persistable(req_opts), resp,
+                                                  api_mode: api_mode, requestor: self,
+                                                  v2_deleted_object: method == :delete && api_mode == :v2)
+      ensure
+        self.class.current_thread_context.active_requestor = old_requestor
+      end
     end
 
     # Execute request without instantiating a new object if the relevant object's name matches the class
@@ -274,17 +280,23 @@ def execute_request_stream(method, path,
               "execute_request_stream requires a read_body_chunk_block"
       end
 
-      params = params.to_h if params.is_a?(RequestParams)
-      http_resp, api_key = execute_request_internal(
-        method, path, base_address, params, opts, usage, &read_body_chunk_block
-      )
+      old_requestor = self.class.current_thread_context.active_requestor
+      self.class.current_thread_context.active_requestor = self
+      begin
+        params = params.to_h if params.is_a?(RequestParams)
+        http_resp, api_key = execute_request_internal(
+          method, path, base_address, params, opts, usage, &read_body_chunk_block
+        )
 
-      # When the read_body_chunk_block is given, we no longer have access to the
-      # response body at this point and so return a response object containing
-      # only the headers. This is because the body was consumed by the block.
-      resp = StripeHeadersOnlyResponse.from_net_http(http_resp)
+        # When the read_body_chunk_block is given, we no longer have access to the
+        # response body at this point and so return a response object containing
+        # only the headers. This is because the body was consumed by the block.
+        resp = StripeHeadersOnlyResponse.from_net_http(http_resp)
 
-      [resp, api_key]
+        [resp, api_key]
+      ensure
+        self.class.current_thread_context.active_requestor = old_requestor
+      end
     end
 
     def store_last_response(object_id, resp)
@@ -297,6 +309,19 @@ def last_response_has_key?(object_id)
       self.class.current_thread_context.last_responses&.key?(object_id)
     end
 
+    # Subclass override point for custom HTTP transports.
+    # Must return an object compatible with Net::HTTPResponse
+    # (.code, .body, .to_hash, .[], .read_body).
+    protected def send_request(method, url, headers, body, query, &response_block)
+      APIRequestor
+        .default_connection_manager(config)
+        .execute_request(method, url,
+                         body: body,
+                         headers: headers,
+                         query: query,
+                         &response_block)
+    end
+
     #
     # private
     #
@@ -524,13 +549,7 @@ def self.maybe_gc_connection_managers
 
       http_resp =
         execute_request_with_rescues(base_url, headers, api_mode, usage, context) do
-          self.class
-              .default_connection_manager(config)
-              .execute_request(method, url,
-                               body: body,
-                               headers: headers,
-                               query: query,
-                               &response_block)
+          send_request(method, url, headers, body, query, &response_block)
         end
 
       [http_resp, opts]
diff --git a/lib/stripe/stripe_client.rb b/lib/stripe/stripe_client.rb
index fb6a89be5..0d0ecba03 100644
--- a/lib/stripe/stripe_client.rb
+++ b/lib/stripe/stripe_client.rb
@@ -24,7 +24,8 @@ def initialize(api_key,
                    uploads_base: nil,
                    connect_base: nil,
                    meter_events_base: nil,
-                   client_id: nil)
+                   client_id: nil,
+                   requestor: nil)
       unless api_key
         raise AuthenticationError, "No API key provided. " \
                                    'Set your API key using "client = Stripe::StripeClient.new(<API-KEY>)". ' \
@@ -46,7 +47,17 @@ def initialize(api_key,
       }.compact
 
       config = StripeConfiguration.client_init(config_opts)
-      @requestor = APIRequestor.new(config)
+      @requestor = if requestor
+                     instance = requestor.call(config)
+                     unless instance.is_a?(APIRequestor)
+                       raise ArgumentError,
+                             "requestor callable must return an APIRequestor instance, " \
+                             "got #{instance.class}"
+                     end
+                     instance
+                   else
+                     APIRequestor.new(config)
+                   end
 
       # top-level services: The beginning of the section generated from our OpenAPI spec
       @v1 = Stripe::V1Services.new(@requestor)
diff --git a/rbi/stripe/stripe_client.rbi b/rbi/stripe/stripe_client.rbi
index 2dc68fa85..cf6ae88a5 100644
--- a/rbi/stripe/stripe_client.rbi
+++ b/rbi/stripe/stripe_client.rbi
@@ -3,6 +3,32 @@
 
 module Stripe
   class StripeClient
+    sig do
+      params(
+        api_key: String,
+        stripe_account: T.nilable(String),
+        stripe_context: T.nilable(String),
+        stripe_version: T.nilable(String),
+        api_base: T.nilable(String),
+        uploads_base: T.nilable(String),
+        connect_base: T.nilable(String),
+        meter_events_base: T.nilable(String),
+        client_id: T.nilable(String),
+        requestor: T.nilable(T.proc.params(config: Stripe::StripeConfiguration).returns(Stripe::APIRequestor))
+      ).void
+    end
+    def initialize( # rubocop:disable Metrics/ParameterLists
+      api_key,
+      stripe_account: nil,
+      stripe_context: nil,
+      stripe_version: nil,
+      api_base: nil,
+      uploads_base: nil,
+      connect_base: nil,
+      meter_events_base: nil,
+      client_id: nil,
+      requestor: nil
+    ); end
     sig do
       params(
         payload: String,
diff --git a/test/stripe/api_requestor_test.rb b/test/stripe/api_requestor_test.rb
index 3d0620081..048430d05 100644
--- a/test/stripe/api_requestor_test.rb
+++ b/test/stripe/api_requestor_test.rb
@@ -35,6 +35,91 @@ class RequestorTest < Test::Unit::TestCase
           assert_equal client, APIRequestor.active_requestor
         end
       end
+
+      should "be set to self during execute_request" do
+        stub_request(:post, "#{Stripe::DEFAULT_API_BASE}/v1/path")
+          .to_return(body: JSON.generate(object: "account"))
+
+        observed_requestor = nil
+        custom_class = Class.new(APIRequestor) do
+          define_method(:send_request) do |method, url, headers, body, query, &block|
+            observed_requestor = self.class.active_requestor
+            super(method, url, headers, body, query, &block)
+          end
+        end
+
+        requestor = custom_class.new("sk_test_123")
+        requestor.execute_request(:post, "/v1/path", :api)
+
+        assert_equal requestor, observed_requestor
+      end
+
+      should "be restored after execute_request completes" do
+        stub_request(:post, "#{Stripe::DEFAULT_API_BASE}/v1/path")
+          .to_return(body: JSON.generate(object: "account"))
+
+        before = APIRequestor.active_requestor
+        requestor = APIRequestor.new("sk_test_123")
+        requestor.execute_request(:post, "/v1/path", :api)
+        assert_equal before, APIRequestor.active_requestor
+      end
+
+      should "be restored after execute_request raises" do
+        before = APIRequestor.active_requestor
+        requestor = APIRequestor.new("sk_test_123")
+
+        assert_raises(Stripe::APIConnectionError) do
+          stub_request(:post, "#{Stripe::DEFAULT_API_BASE}/v1/path")
+            .to_raise(Errno::ECONNREFUSED)
+          requestor.execute_request(:post, "/v1/path", :api)
+        end
+
+        assert_equal before, APIRequestor.active_requestor
+      end
+    end
+
+    context "#send_request" do
+      should "be called during normal request flow" do
+        stub_request(:post, "#{Stripe::DEFAULT_API_BASE}/v1/path")
+          .to_return(body: JSON.generate(object: "account"))
+
+        called = false
+        custom_class = Class.new(APIRequestor) do
+          define_method(:send_request) do |method, url, headers, body, query, &block|
+            called = true
+            super(method, url, headers, body, query, &block)
+          end
+        end
+
+        requestor = custom_class.new("sk_test_123")
+        requestor.execute_request(:post, "/v1/path", :api)
+
+        assert called
+      end
+
+      should "allow subclass to override transport" do
+        mock_response = Struct.new(:code, :body, keyword_init: true) do
+          def to_hash
+            { "content-type" => ["application/json"] }
+          end
+
+          def [](name)
+            to_hash[name.downcase]&.first
+          end
+        end
+
+        response = mock_response.new(code: "200", body: JSON.generate(object: "account", id: "acct_mock"))
+        custom_class = Class.new(APIRequestor) do
+          define_method(:send_request) do |_method, _url, _headers, _body, _query, &_block|
+            response
+          end
+        end
+
+        requestor = custom_class.new("sk_test_123")
+        result = requestor.execute_request(:get, "/v1/accounts/acct_mock", :api)
+
+        assert_equal "acct_mock", result.id
+      end
     end
 
     context ".maybe_gc_connection_managers" do
diff --git a/test/stripe/stripe_client_test.rb b/test/stripe/stripe_client_test.rb
index 121f7fe68..b930b91a8 100644
--- a/test/stripe/stripe_client_test.rb
+++ b/test/stripe/stripe_client_test.rb
@@ -13,6 +13,73 @@ class StripeClientTest < Test::Unit::TestCase
         assert client.instance_variable_get(:@requestor).is_a?(APIRequestor)
         assert client.instance_variable_get(:@requestor).config.api_key == "sk_test_123"
       end
+
+      should "use default APIRequestor when no requestor given" do
+        client = StripeClient.new("sk_test_123")
+        assert_equal APIRequestor, client.instance_variable_get(:@requestor).class
+      end
+
+      should "accept a requestor factory callable" do
+        custom_class = Class.new(APIRequestor)
+        factory = ->(config) { custom_class.new(config) }
+        client = StripeClient.new("sk_test_123", requestor: factory)
+        assert_instance_of custom_class, client.instance_variable_get(:@requestor)
+      end
+
+      should "pass config to requestor factory callable" do
+        received_config = nil
+        factory = lambda do |config|
+          received_config = config
+          APIRequestor.new(config)
+        end
+        StripeClient.new("sk_test_123", stripe_account: "acct_abc", requestor: factory)
+        assert_equal "sk_test_123", received_config.api_key
+        assert_equal "acct_abc", received_config.stripe_account
+      end
+
+      should "reject requestor that does not return APIRequestor" do
+        factory = ->(_config) { Object.new }
+        assert_raises(ArgumentError) do
+          StripeClient.new("sk_test_123", requestor: factory)
+        end
+      end
+    end
+
+    context "custom requestor" do
+      setup do
+        @send_request_calls = []
+        calls = @send_request_calls
+        @custom_requestor_class = Class.new(APIRequestor) do
+          define_method(:send_request) do |method, url, headers, body, query, &response_block|
+            calls << { method: method, url: url }
+            super(method, url, headers, body, query, &response_block)
+          end
+        end
+      end
+
+      should "route v1 service calls through custom transport" do
+        stub_request(:get, "#{Stripe::DEFAULT_API_BASE}/v1/customers")
+          .to_return(body: JSON.generate(object: "list", data: []))
+
+        factory = ->(config) { @custom_requestor_class.new(config) }
+        client = StripeClient.new("sk_test_123", requestor: factory)
+        client.v1.customers.list
+
+        assert_equal 1, @send_request_calls.length
+        assert_equal :get, @send_request_calls[0][:method]
+        assert_includes @send_request_calls[0][:url], "/v1/customers"
+      end
+
+      should "route raw_request through custom transport" do
+        stub_request(:get, "#{Stripe::DEFAULT_API_BASE}/v1/customers")
+          .to_return(body: JSON.generate(object: "list", data: []))
+
+        factory = ->(config) { @custom_requestor_class.new(config) }
+        client = StripeClient.new("sk_test_123", requestor: factory)
+        client.raw_request(:get, "/v1/customers")
+
+        assert_equal 1, @send_request_calls.length
+      end
     end
 
     context "StripeClient config" do